Wettability control of silicon by creating sub-30 nm nanopillars via self- assembled block copolymer templates and polymer brush deposition

Superhydrophobic surfaces in the so-called Cassie or non-wetting state display extreme wetting behavior through a combination of surface texture and hydrophobic surface chemistry that can cause water droplets to roll or bounce off, carrying away dust particle and other contaminants in the process. Potential applications for these surfaces range from self-cleaning surfaces to water condensation surfaces for enhancing energy efficiency in power generation and water desalination. In nature, we find biological systems that combine material properties and texture to achieve specific functionality. Examples include the anti-wetting and self-cleaning properties of the Lotus leaf, the anti-dew properties of the Dog's Bane leaf and the anti-reflective properties of insect's eyes. These examples highlight that designing functional surfaces often requires the geometrical control of surface feature shape, size and periodicity at nanometric length scales. However, fabricating increasingly smaller nanostructures (below 30 nm), while maintaining precise geometric control over large areas presents a significant challenge.